As the sizes of semiconductor integrated circuits and the design rule for line widths have decreased, the issue of contamination of the devices and substrates or wafers during processing has become more important. The demand for extremely clean processing environments for these devices has increased. As sizes of wafers has increased, for example, from 200 mm diameter wafers to 300 mm wafers, fully automated systems have also become a requirement for processing the wafers. The area of a 300 mm wafer is 2.25 times larger than the area of a 200 mm wafer, and the 300 mm wafer is about 2.2 times heavier than a 200 mm wafer. These increases in wafer size and weight and in the demand for cleaner processing environments have led to the requirement for complete automation of wafer processing.
The SEMI Standard provides standards for semiconductor processes and processing equipment. For example, the SEMI Standard defines an Equipment Front End Module (EFEM), which includes a wafer or substrate carrier handler that receives wafer carriers from the factory material handling system at one or more of its load ports (as specified in SEMI E15.1). The EFEM generally includes load ports for receiving the carriers, a transfer unit and a frame or “mini-environment.”
A conventional open-type wafer container is typically exposed to the clean room environment. As a result, the entire clean room conventionally was maintained at the required cleanliness of the wafers. As the cleanliness requirements have become more stringent, maintaining an acceptable clean room has become extremely expensive. A closed-type wafer container can separate environments in the clean room by preventing exposure of the wafers in the container to the clean room environment. A front opening unified pod (FOUP) is one type of closed-type wafer container.
U.S. Pat. No. 6,074,154 discloses a conventional substrate processing system with a substrate transfer system. U.S. Pat. No. 6,032,704 discloses a conventional wafer storage container or pod used in wafer processing systems. Both of these U.S. patents are incorporated herein in their entirety by reference.
FIG. 1 contains a schematic top view of a manufacturing process system or tool 10 having an EFEM 40. The EFEM includes a frame 12 and a plurality of wafer pod load stations 14. An interface wall 16 separates the clean room 18 from the gray area 20 where the processing system 10 is housed. A single wafer process tool may include one or more load lock chambers 22, a central transfer chamber 24 and a plurality of processing chambers 26 mounted on the transfer chamber 24. A robot 28 disposed in the frame 12 moves wafers from wafer pods disposed on the pod loading stations 14 into the load lock chamber 22. A robot 30 disposed in the transfer chamber 24 moves wafers from the load chamber 22 into the processing chamber 26. The pod load stations 14 receive the pods (FOUPs), and the wafers carried in the FOUPs are transferred into the frame 12 and the wafer process equipment 10.
FIG. 2 contains a cross-sectional view of the processing system 10 and EFEM 40 having a fan 42 and a filter 44 which intake air into a wafer handling zone of the EFEM 40. When a silicon wafer is exposed to air, an undesired native oxide is grown. In a conventional system, to reduce the oxide grown, the fan 42 can inject an inert gas instead of air into the EFEM 40. However, the cost for this approach is very high. A wafer container or pod (FOUP) 13 is mounted on a port 14 of the EFEM 40. The EFEM 40 includes a platform 15 on which wafers transferred from the pod 13 can be mounted.
A wafer container having an injector of inert gas is described in U.S. Pat. No. 6,032,704, incorporated by reference above. However, a drawback of this technology is that the handler or EFEM or the wafer container have a complicated configuration and high cost.